textproduct: Rapid City

KEY MESSAGES

- Another round of rain, with snow in Black Hills, is likely later tonight into Monday.

- Much colder to start the week but warmer temps return by late week.

- Low-end chances for rain return later this week.

DISCUSSION

(Tonight Through Sunday) Issued at 1051 PM MDT Sun May 17 2026

Upper air analysis depicts upper trof digging into the Intermountain West with southwest flow across the Northern Plains. Water vapor imagery shows moisture associated with our next system making its way into the area. Precip chances will increase overnight across northeastern WY, the Black Hills, and southwestern SD as this system approaches from the southwest. Precip will overspread the region Monday as band of 850-700mb FGEN and plenty of available moisture sets up over much of the CWA. Expecting mainly rain over the western SD plains with snow over the Black Hills. Northeastern WY could see snow to start out with with a change over to rain in the afternoon as the day warms up.

There's still some uncertainty as to where the strongest forcing (and therefore the highest precip amounts) will be, right now it looks like the greatest precip totals will be across the Northern Black Hills and southwestern SD into the western SD plains with total QPF amounts of up to 0.25 to 0.4 inches are likely. Froude numbers of around 1 and moist, northerly flow will support upslope snow across the northern Black Hills. However, given the time of year and the fact that the snow is going to be falling during the day, snow accumulations (especially on roadways) may be limited by melting. Therefore, anticipating slushy accumulations of up to 3-5", mainly on grassy sfcs and in the higher elevations of the Black Hills. Northeastern WY could also see light snow accumulations with this system though, again, the time of year and the fact that this will be occurring during the daytime will limit overall snow totals. Expecting around a trace to up to 2 inches with the highest amounts across southern Campbell County. Regardless of final snow amounts, the main thing to note is that much of the area will receive some much needed moisture.

Below normal temps expected through early this week with lows tonight, Monday, and Tuesday nights dropping into the 20s to 30s. A Freeze Warning remains in effect for northeastern WY for early this morning as temps are expected to drop into the upper 20s. Additional Frost/Freeze headlines may be needed for Monday and Tuesday nights, but will hold off on issuance for now. Shortwave ridging develops by the mid-week and kick off a gradual warming trend for the rest of the week. Approaching upper trof then brings precip chances back to the CWA for the late week.

AVIATION

(For the 06Z TAFS Through 06Z Monday Night) Issued At 1111 PM MDT Sun May 17 2026

A disturbance will bring deteriorating flight conditions to the entire forecast area by 18/12z with widespread MVFR/IFR conditions developing. Local LIFR conditions may occur in/near the Black Hills due to snow. Conditions will slowly improve after 18/22z.

UNR WATCHES/WARNINGS/ADVISORIES

SD...WY...Freeze Warning from 5 AM to 10 AM MDT Monday for WYZ054>056- 058>060.